Northwest Oyster Die-offs Show Ocean Acidification Has Arrived

The acidification of the world’s oceans from an excess of CO2 has already begun, as evidenced recently by the widespread mortality of oyster larvae in the Pacific Northwest. Scientists say this is just a harbinger of things to come if greenhouse gas emissions continue to soar

It was here, from 2006 to 2008, that oyster larvae began dying dramatically, with hatchery owners Mark Wiegardt and his wife, Sue Cudd, experiencing larvae losses of 70 to 80 percent. “Historically we’ve had larvae mortalities,” says Wiegardt, but those deaths were usually related to bacteria. After spending thousands of dollars to disinfect and filter out pathogens, the hatchery’s oyster larvae were still dying.

Finally, the couple enlisted the help of Burke Hales, a biogeochemist and ocean ecologist at Oregon State University. He soon homed in on the carbon chemistry of the water. “My wife sent a few samples in and Hales said someone had screwed up the samples because the [dissolved CO2 gas] level was so ridiculously high,” says Wiegardt, a fourth-generation oyster farmer. But the measurements were accurate. What the Whiskey Creek hatchery was experiencing was acidic seawater, caused by the ocean absorbing excessive amounts of CO2 from the air.

Ocean acidification — which makes it difficult for shellfish, corals, sea urchins, and other creatures to form the shells or calcium-based structures they need to live — was supposed to be a problem of the future. But because of patterns of ocean circulation, Pacific Northwest shellfish are already on the front lines of these potentially devastating changes in ocean chemistry. Colder, more acidic waters are welling up from the depths of the Pacific Ocean and streaming ashore in the fjords, bays, and estuaries of Oregon, Washington, and British Columbia, exacting an environmental and economic toll on the region’s famed oysters.

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-Research thanks to Tony H.


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